A new study led by researchers at Los Alamos National Laboratory made a major advance in quantum dot laser technology: the demonstration of low-threshold, continuous-wave (CW) lasing using solution-processed colloidal quantum dots. The achievement, published in Nature Photonics, could significantly accelerate the development of practical, compact, and energy-efficient quantum dot lasers for on-chip and integrated photonic systems.
“This work represents an important technical milestone that significantly advances what can be achieved with solution-processed nanomaterials,” said Victor Klimov, leader of the Nanotechnology and Advanced Spectroscopy Team and the project’s principal investigator. “We can now realistically envision quantum dot lasers that operate continuously, efficiently, and across a wide color range, paving the way for transformative photonic applications.”
For more than three decades, colloidal quantum dots — semiconductor nanocrystals synthesized in liquid — have been studied as promising, tunable light sources. But achieving stable CW lasing is still a challenge because of the extremely high optical intensities required, which leads to sample overheating and rapid degradation. The Los Alamos team overcame these limitations by designing a new class of quantum dots called type-(I+II) quantum dot heterostructures, which combine the properties of both spatially direct and indirect nanostructures within a single nanocrystal. The researchers demonstrated that lasers operating with low power thresholds show significant improvement over previous CW quantum dot lasers. “This is the first time a solution-processed colloidal system has reached such a low threshold under continuous excitation, while maintaining stable lasing performance,” said Donghyo Hahm, the study’s lead author and a postdoctoral researcher at Los Alamos.
The exceptional gain performance of type-(I+II) quantum dots stems from their unique hybrid direct/indirect electronic structure. In these nanocrystals, one exciton resides in a direct configuration that radiates efficiently, while another remains spatially separated, or indirect, stabilizing the multicarrier state and prolonging optical gain.
Beyond CW lasing, the team also demonstrated the versatility of these type-(I+II) quantum dots by realizing lasing in two additional device architectures: a fully stacked electroluminescent cavity-based device, representing a prototype for a quantum dot laser diode, and an on-chip microdisk laser.
Together, these results showcase a unified materials platform capable of supporting multiple lasing applications — from continuous to ultrafast pulsed operation — using the same quantum dot design.
“This work represents a significant step forward for colloidal nanomaterials,” said Valerio Pinchetti, a Director’s Postdoctoral Fellow and spectroscopy expert at Los Alamos. “By making solution-processed quantum dots lasing ready under low-power conditions, we are bridging the gap between laboratory demonstrations and scalable photonic technologies.”
The ability to achieve CW lasing with simple, low-cost laser diodes as a pump source opens the door to a new generation of compact, tunable, and energy-efficient quantum dot light sources. These could be integrated into photonic chips, optical interconnects, or sensing platforms where traditional high-power or vacuum-fabricated semiconductor lasers are impractical.
Paper: “Low-Threshold Lasing from Colloidal Quantum Dots under Quasi-Continuous-Wave Excitation,” Nature Photonics (2025).
Funding: Supported by the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
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